I am starting a pattern I purchased from KP and the beginning reads like this:

Pattern Notes:
• Th ese gloves are knit fl at in a ribbed pattern and seamed up the side. An extra stitch
(called a selvage stitch) is added to each side of the piece. If seamed properly using the
Mattress Stitch, these selvage stitches will be invisible after the gloves are completed.
• To ensure that the bottom and top edges are not too tight, it is important to cast on
and cast off loosely. One way to accomplish this is by using a needle one or two sizes
larger to work the cast on and cast off rows.

Okay, I know what a selvage is but what I don't understand is if I am to knit or slip the selvage stitch? I have CO twice and attempted to knit the first row--both times I've ended up with too many or not enough stitches to stay in pattern. I have followed the pattern as written and I've slipped the first stitch...the problem is--the pattern never equals 47 stitches. Do I cast on additional stitches to make the selvage stitch at each end? I'm so confused--even if I CO two additional stitches (to use as the selvage stitch on each end), I still don't come up with the correct number of stitches. The repeat is a 5 stitch pattern and the pattern calls for 4 additional stitches (K1, P1 at the beginning and P1, K1 at the end). This can never equal 47. If I add two stitches I'll technically have 49--again, this pattern can't be spread evenly across 49 stitches...What am I missing here? I feel so dumb!